The Preparation Of Fluorescent Silica PH Nano-sensor And Its Biological Applications

pH is a commonly measured parameter in many applications such as environmental monitoring, bioprocessing, and biomedical diagnostics. Optical, in particular fluorescent pH sensors have proved to be reliable alternatives to glass electrodes and have become very popular analytical tools in the last decades. The most important element of the optical pH sensor is the sensitive probe. In this thesis, novel carboxylate-modified fluorescent silica pH nanosensors were synthesized using a reverse microemulsion method with a pH sensitive squaraine dye used as pH indicator. This pH sensitive squaraine dye was simply doped inside SiNPs without any complicated procedures. To avoid aggregation among the particles and to increase the water solubility of the pH nanosensors, the SiNPs were surface modified with a carboxyl group. This pH probe exhibits a good linear dynamic response between pH 3.01 and 5.72. Many alkali, alkaline earth, and transitional metal ions including Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Al3+, V5+, Cr3+, Cr6+, Mn2+, Fe2+, Fe3+, Co2+, Ni3+, Cu2+, Zn2+, As3+, Se4+, Mo6+, Ag+, Cd2+, La3+. Er3+. Ir3+, Hg+, Hg2+ and Pb2+ had no significant interference on pH value determination. Four buffer systems have been used, including deionized water, Britton-Robison (BR, H3PO4-HAc-H3BO3 and NaOH) buffer, Tris-HCl and phosphate (KH2PO4-Na2HPO4) buffer. And they have no effect on the application of this pH nanosensor. Below the temperature of 50 centigrade, its fluorescent intensity has tiny variety, and can hold the stability for a long time. Artificial sample determination showed that the pH nanosensors developed in this thesis possess a very promising applicability in biological and biomedical fields. In addition, we attempt to use this sensor to monitor the process of enzyme hydrolysis, and the results were perfect.